Japanese Patent Laying-Open No. 2015-33003 (PTD 1) discloses one configuration example of an optical unit (ONU). This ONU includes a variable wavelength optical transceiver, a physical (PHY)/media access control (MAC) processing unit, and a user network interface (UNI) processing unit. One PHY/MAC processing unit is provided and one UNI processing unit is provided.
For example, Japanese Patent Laying-Open No. 2007-243861 (PTD 2) discloses an ONU including a plurality of UNI ports. Japanese Patent Laying-Open No. 2015-33003 and Japanese Patent Laying-Open No. 2014-155177 (PTD 3) disclose an OLT having a plurality of MAC processing units.